A keratinolytic protease-producing microorganism was isolated from soybean paste waste and was identified as a strain of Bacillus sp. The keratinase was purified by polyethylene glycol precipitation and two successive column chromatographies with DEAE-Toyopearl 650C and Sepliacryl S-200 HR. The purified enzyme had overall 11 purification folds with an 18% yield. The results of sodium dodecyl sulfate polyacrylamide gel electrophoresis and gel filtration on Sephacryl G-200 indicated that the purified enzyme was monomeric and had a molecular weight of 134 kDa. The optimum temperature and pH were 40degreesC and 7.0, respectively. This enzyme was completely inhibited by EDTA and EGTA, and it was restored by the addition of Ca+2 and Mg+2. These results suggested that it is a metalloprotease. The stimulated enzyme activity by reducing agents indicated that the reducing condition was important in the expression of the activity.